Water Resources System Network building for Climate Change I As the impacts of climate change wield significant influence on human life as well as the ecosystem, the issue of global climate change among all the threatening environment problems of the 21st century has begun to attract the greatest attraction. In recent years, there has been evidence that global climate change precipitated by temporal and seasonal variations of rainfall will have significant effects on water resources, and the potential damage from climate change has been expected to increase exponentially. Projecting regional impacts of climate change and variability relies on General Circulation Models (GCMs), and previous research has focused mostly on the regional hydrological impacts, with only a limited number studies conducted on water resources systems. To counter this problem, the objective of this study is to build a dynamic network of water resources systems reflecting the current water rights system in order to project regional climate change impacts on the water supply system and to devise adaptation strategies for reducing vulnerability to future water shortage problems. In this vein, the impacts of climate change on the water supply system in the Nakdong River basin have been investigated, with the time frame for assessing the impacts of climate change designated as from 2010 to 2100. An increase in water demand and environmental changes in the Nakdong River basin due to the Four-River Restoration Project will also have significant impacts on the water resource management system in the basin. To build a dynamic network of the water resources system, water usage was first examined based on annual statistical almanacs, and the withdrawal point as well as return point were identified. Understanding the effects of climate change on prospective water supply and demand requires climate scenarios; therefore, CSIRO-MK3.0 with A1b (emission scenarios) were selected to simulate the future climate and baseline climate data. As rainfall and temperature are the two climatic variables driving the water supply system, both variables were simulated by statistical down-scale approach. As expected, the magnitude and direction of changes in rainfall varied from region to region. Next, by using the rainfall-runoff model to estimate natural stream flow from climate scenarios, the study attempted to evaluate how climate change impacts may affect, and be affected by, the water supply system in the Nakdong River basin. The results showed that climate variation yields water shortage to a greater severity than climate change introduced by emission scenarios. Following, the effects of raising irrigation reservoir banks as part of the Four River Restoration Project were evaluated. The study was carried out in the two sub-basins in the Nakdong River basin. The results showed that the additional water supply for instream flow in conjunction with preserving the water volume by raising reservoir banks will contribute to the overall water quantity as well as the quality of downstream. However, maintaining better water quality in irrigation reservoirs is important because the water quality of irrigation reservoirs will have impact on the water quality of not only the downstream of reservoirs, but also the main stream of the Nakdong River basin. Based on the aforementioned findings, the current study forwarded several policy recommendations. First, the central as well as local governments should evaluate the impacts of climate change by building a dynamic water resources system model and encouraging the formation of flexible institutions for water allocation by water resources networking. Second, the current water rights system for climate change should be reevaluated as conflicts by water shortage are highly likely to arise in light of climate change. Third, the government should improve not only hydrologic monitoring, but also the water usage monitoring system. The agency in charge of hydraulic structures should explore their vulnerability and exercise measures to mitigate the impacts of climate change.